Civ4 is one of the more open ended games out there for me - three or more years on, and I'm still playing it every week. Just brilliant. Not "endless" as such, but each and every game plays out very differently. However, it's the pacing that allows you to have a full-on game that'll take a month to play. Set it up for hard, with 18 enemy Civ's on Marathon - and you've got an epic right there!

If you're looking for true endlessness with a space theme - you might want to take a look at EVE Online. Truly endless, and truly open. Pay per month though, so maybe not your thing.

I know what you mean - it may (maybe not) be worth your while looking at Fallout 3. If you play it as a linear game - go there, do this, repeat - you'll finish it in two days. Play it as I am, as in an exploration and scavenging game, and it's sheer scale will astound you. I've been at it since the start of November, and still have a long long way to go. It's about as un-linear as you can possibly get, with the exception of EVE Online - that's just ridiculous!

Fallout 3 is "essentially" (in all the good and none of the bad ways) Oblivion with guns - if you want never ending awesome gameplay, and don't mind some sword and spell action, Oblivion is one of the best there is. The mods out there are just breathtaking, and make the game so much more than it could have ever been from a studio - just superb. Fallout 3 is getting there with the mods, but it'll take a while more.

Yeah thanks Spec. I did that with STALKER. Just took my time and went through it slowly. I don't like to rush games like that.
Oblivion sounds good. I might have a look at that.
Also X3 I read a article that said that it was very big.
Hmmm interesting options.

X3 is huge and you can get some spectacular battles going on but you better have some serious hardware to back it up. All those particle bursts and hundred or more space ships all trying to blast one another into space debris takes a heavy toll on the video card. The thing with X3 is it could take you months just to get your manufacturing base up and running to put out your ships, weapons, shields and ammo. Then you need to protect those factories and resources. Then you can go and start a war with any or all the races, but make sure you have all the factories and such that you want first because once you start a war with say the Teladi, you can't buy any more factories from them, so make sure you have enough Space Fuel factories to keep the pirates happy.